The soil microbe Bacillus thuringiensis (B.t.) is a Gram-positive, spore-forming bacterium. Most strains of B.t. do not exhibit pesticidal activity. Some B.t. strains produce, and can be characterized by, parasporal crystalline protein inclusions. These xe2x80x9cxcex4-endotoxinsxe2x80x9d are different from exotoxins, which have a non-specific host range. These inclusions often appear microscopicallyas distinctively shaped crystals. The proteins can be highly toxic to pests and specific in their toxic activity. Certain B.t. toxin genes have been isolated and sequenced, and recombinant DNA-based B.t. products have been produced and approved for use. In addition, with the use of genetic engineering techniques, new approaches for at delivering B.t. toxins to agricultural environments are under development, including the use of plants genetically engineered with B.t. toxin genes for insect resistance and the use of stabilized intact micro bial cells as B.t. toxin delivery vehicles (Gaertner, F. H., L. Kim [1988] TIBTECH 6:S4-S7). Thus, isolated B.t. endotoxin genes are becoming commercially valuable.
Until the last fifteen years, commercial use of B.t. pesticides has been largely restricted to a narrow range of lepidopteran (caterpillar) pests. Preparations of the spores and crystals of B. thuringiensis subsp. kurstaki have been used for many years as commercial insecticides for lepidopteran pests. For example, B. thuringiensis var. kurstaki HD-1 produces a crystalline xcex4-endotoxin which is toxic to the larvae of a number of lepidopteran insects.
In recent years, however, investigators have discovered B.t. pesticides with specificities for a much broader range of pests. For example, other species of B.t., namely israelensis and morrisoni (a.k.a. tenebrionis, a.k.a. B.t. M-7, a.k.a. B.t. san diego), have been used commercially to control insects of the orders Diptera and Coleoptera, respectively (Gaertner, F. H. [1989] xe2x80x9cCellular Delivery Systems for Insecticidal Proteins: Living and Non-Living Microorganisms,xe2x80x9d in Controlled Delivery of Crop Protection Agents, R. M. Wilkins, ed., Taylor and Francis, New York and London, 1990, pp. 245-255.). See also Couch, T. L. (1980) xe2x80x9cMosquito Pathogenicity of Bacillus thuringiensis var. israelensis,xe2x80x9d Developments in Industrial Microbiology 22:61-76; and Beegle, C. C. (1978) xe2x80x9cUse of Entomogenous Bacteria in Agroecosystems,xe2x80x9d Developments in Industrial Microbiology 20:97-104. Krieg, A., A. M. Huger, G. A. Langenbruch, W. Schnetter (1983) Z. ang. Ent. 96:500-508 describe Bacillus thuringiensis var. tenebrionis, which is reportedly active against two beetles in the order Coleoptera. These are the Colorado potato beetle, Leptinotarsa decemlineata, and Agelastica alni. Microbiological Reviews 52(2):242-255). Hxc3x6fte and Whiteley classified B.t. crystal protein genes into four major classes. The classes were CryI (Lepidoptera-specific), CryII (Lepidoptera- and Diptera-specific), CryIII (Coleoptera-specific), and CryIV (Diptera-specific). The discovery of strains specifically toxic to other pests has been reported (Feitelson, J. S., J. Payne, L. Kim [1992] Bio/Technology 10:271-275). CryV has been proposed to designate a class of toxin genes that are nematode-specific. Lambert et al. (Lambert, B., L. Buysse, C. Decock, S. Jansens, C. Piens, B. Saey, J. Seurinck, K. van Audenhove, J. Van Rie, A. Van Vliet, M. Peferoen [1996] Appl. Environ. Microbiol 62(1):80-86) and Shevelevet al. ([1993]FEBS Lett. 336:79-82) describe the characterization of Cry9 toxins active against lepidopterans. Published PCT applications WO 94/05771 and WO 94/24264 also describe B.t. isolates active against lepidopteran pests. Gleave et al. ([1991] JGM 138:55-62) and Smulevitch et al. ([1991] FEBS Lett. 293:25-26) also describe B.t. toxins. A number of other classes of B.t. genes have now been identified.
The cloning and expression of a B.t. crystal protein gene in Escherichia coli has been described in the published literature (Schnepf, H. E., H. R. Whiteley [1981] Proc. Natl. Acad. Sci. USA 78:2893-2897.). U.S. Pat. No. 4,448,885 and U.S. Pat. No. 4,467,036 both disclose the expression of B.t. crystal protein in E. coli. U.S. Pat. Nos. 4,990,332; 5,039,523; 5,126,133; 5,164,180; and 5,169,629 are among those which disclose B.t. toxins having activity against lepidopterans. PCT application WO96/05314 discloses PS86W1, PS86V1, and other B.t. isolates active against lepidopteran pests. The PCT patent applications published as WO94124264 and WO94105771 describe B.t. isolates and toxins active against lepidopteran pests. B.t. proteins with activity against members of the family Noctuidae are described by Lambert et al., supra. U.S. Pat. Nos. 4,797,276 and 4,853,331 disclose B. thuringiensis strain tenebrionis which can be used to control coleopteran pests in various environments. U.S. Pat. No. 4,918,006 discloses B.t. toxins having activity against dipterans. U.S. Pat. No. 5,151,363 and U.S. Pat. No.4,948,734 disclose certain isolates of B.t. which have activity against nematodes. Other U.S. patents which disclose activity against nematodes include 5,093,120; 5,236,843; 5,262,399; 5,270,448; 5,281,530; 5,322,932; 5,350,577; 5,426,049; and 5,439,881. As a result of extensive research and investment of resources, other patents have issued for new B.t. isolates and new uses of B.t. isolates. See Feitelson et al., supra, for a review. However, the discovery of new B.t. isolates and new uses of known B.t. isolates remains an empirical, unpredictable art.
Isolating responsible toxin genes has been a slow empirical process. Carozzi et al. (Carozzi, N. B., V. C. Kramer, G. W. Warren, S. Evola, G. Koziel (1991) Appl. Env. Microbiol. 57(11):3057-3061) describe methods for identifing nove B.t. isolates. This report does not disclose or suggest the specific primers, probes, toxins, and genes of the subject invention for lepidopteran-active toxin genes. U.S. Pat. No. 5,204,237 describes specific and universal probes for the isolation of B.t. toxin genes. This patent, however, does not describe the probes, primers, toxins, and genes of the subject invention.
WO 94/21795 and Estruch, J. J. et al. ([1996] PNAS 93:5389-5394) describe toxins obtained from Bacillus microbes. These toxins are reported to be produced during vegetative cell growth and were thus termed vegetative insecticidal proteins (VIP). These toxins were reported to be distinct from crystal-fornming xcex4-endotoxins. Activity of these toxins against lepidopteran pests was reported.
Black cutworm (Agrotis ipsilon (Hufnagel); Lepidoptera: Noctuidae) is a serious pest of many crops including maize, cotton, cole crops (Brassica, broccoli, cabbages, Chinese cabbages), and turf. Secondary host plants include beetroots, Capsicum (peppers), chickpeas, faba beans, lettuces, lucerne, onions, potatoes, radishes, rape (canola), rice, soybeans, strawberries, sugarbeet, tobacco, tomatoes, and forest trees. In North America, pests of the genus Agrotis feed on clover, corn, tobacco, hemp, onion, strawberries, blackberries, raspberries, alfalfa, barley, beans, cabbage, oats, peas, potatoes, sweetpotatoes, tomato, garden flowers, grasses, lucerne, maize, asparagus, grapes, almost any kind of leaf, weeds, and many other crops and garden plants. Other cutworms in the Tribe Agrotini are pests, in particular those in the genus Feltia (e.g., F. jaculifera (Guenxc3xa9e); equivalent to ducens subgothica) and Euxoa (e.g., E. messoria (Harris), E. scandens (Riley), E. auxiliaris Smith, E. detersa (Walker), E. tessellata (Harris), E. ochrogaster (Guenxc3xa9e). Host plants include various crops, including rape.
Cutworms are also pests outside North America, and the more economically significant pests attack chickpeas, wheat, vegetables, sugarbeet, luceme, maize, potatoes, turnips, rape, lettuces, strawberries, loganberries, flax, cotton, soybeans, tobacco, beetroots, Chinese cabbages, tomatoes, aubergines, sugarcane, pastures, cabbages, groundnuts, Cucurbita, turnips, sunflowers, Brassica, onions, leeks, celery, sesame, asparagus, rhubarb, chicory, greenhouse crops, and spinach. The black cutworm A. ipsilon occurs as a pest outside North America, including Central America, Europe, Asia, Australasia, Africa, India, Taiwan, Mexico, Egypt, and New Zealand.
Cutworms progress through several instars as larvae. Although seedling cutting by later instar larvae produces the most obvious damage and economic loss, leaf feeding commonly results in yield loss in crops such as maize. Upon reaching the fourth larval instar, larvae begin to cut plants and plant parts, especially seedlings. Because of the shift in feeding behavior, economically damaging populations may build up unexpectedly with few early warning signs. Their nocturnal habit and behavior of burrowing into the ground also makes detection problematic. Large cutworms can destroy several seedlings per day, and a heavy infestation can remove entire stands of crops.
Cultural controls for A. ipsilon such as peripheral weed control can help prevent heavy infestations;however, such methods are not always feasible or effective. Infestations are very sporadic, and applying an insecticide prior to planting or at planting has not been effective in the past. Some baits are available for control of cutworms in crops. To protect turfgrass such as creeping bentgrass, chemical insecticides have been employed. Use of chemical pesticides is a particular concern in turf because of the close contact the public has with treated areas (e.g., golf greens, athletic fields, parks and other recreational areas, professional landscaping, home lawns). Natural products (e.g., nematodes, azadirachtin) generally perform poorly. To date, Bacillus thuringiensis products have not been widely used to control black cutworm because highly effective toxins have not been available.
The subject invention concerns materials and methods useful in the control of non-mammalian pests and, particularly, plant pests. In a specific embodiment, the subject invention provides new toxins usefull for the control of lepidopterans. In a particularly preferred embodiment, the toxins of the subject invention are used to control black cutworm. The subject invention further provides nucleotide sequences which encode the lepidopteran-active toxins of the subject invention. The subject invention further provides nucleotide sequences and methods usefull in the identification and characterization of genes which encode pesticidal toxins. The subject invention further provides new Bacillus thuringiensis isolates having pesticidal activities.
In one embodiment, the subject invention concerns unique nucleotide sequences which are useful as primers in PCR techniques. The primers produce characteristic gene fragments which can be used in the identification and isolation of specific toxin genes. The nucleotide sequences of the subject invention encode toxins which are distinct from previously-described xcex4-endotoxins. In one embodiment of the subject invention, B.t. isolates can be cultivated under conditions resulting in high multiplication of the microbe. After treating the microbe to provide single-stranded genomic nucleic acid, the DNA can be contacted with the primers of the invention and subjected to PCR amplification. Characteristic fragments of toxin-encoding genes will be amplified by the procedure, thus identifying the presence of the toxin-encoding gene(s).
A further aspect of the subject invention is the use of the disclosed nuclebtide sequences as probes to detect, identify, and characterize genes encoding B.t. toxins which are active against lepidopterans.
Further aspects of the subject invention include the genes and isolates identified using the methods and nucleotide sequences disclosed herein. The genes thus identified encode toxins active against lepidopterans. Similarly, the isolates will have activity against these pests.
New pesticidal B.t. isolates of the subject invention include PS31G1, PS185U2, PS11B, PS218G2, PS213E5, PS28C, PS86BB 1, PS89J3, PS94R1, PS27J2, PS101DD, and PS202S.
As described herein, the toxins useful according to the subject invention may be chimeric toxins produced by combining portions of multiple toxins.
In a preferred embodiment, the subject invention concerns plants cells transformed with at least one polynucleotide sequence of the subject invention such that the transformed plant cells express pesticidal toxins in tissues consumed by the target pests. Such transformation of plants can be accomplished using techniques well known to those skilled in the art and would typically involve modification of the gene to optimize expression of the toxin in plants.
Alternatively, the B.t. isolates of the subject invention, or recombinant microbes expressing the toxins described herein, can be used to control pests. In this regard, the invention includes the treatment of substantially intact B.t. cells, and/or recombinant cells containing the expressed toxins of the invention, treated to prolong the pesticidal activity when the substantially intact cells are applied to the environment of a target pest. The treated cell acts as a protective coating for the pesticidal toxin. The toxin becomes active upon ingestion by a target insect.
SEQ ID NO. 1 is a forward primer useful according to the subject invention.
SEQ ID NO. 2 is a reverse primer usefull according to the subject invention.
SEQ ID NO. 3 is a forward primer useful according to the subject invention.
SEQ ID NO. 4 is a reverse primer useful according to the subject invention.
SEQ ID NO. 5 is a forward primer useful according to the subject invention.
SEQ ID NO. 6 is a reverse primer useful according to the subject invention.
SEQ ID NO. 7 is an amino acid sequence of the toxin designated 11B1AR.
SEQ ID NO. 8 is a nucleotide sequence encoding an amino acid sequence of toxin 11B1AR (SEQ ID NO. 7).
SEQ ID NO. 9 is an amino acid sequence of the toxin designated 11 B1BR.
SEQ ID NO. 10 is a nucleotide sequence encoding an amino acid sequence of toxin 11B1BR (SEQ ID NO. 9).
SEQ ID NO. 11 is an amino acid sequence of the toxin designated 1291A.
SEQ ID NO. 12 is a nucleotide sequence encoding an amino acid sequence of toxin 1291A (SEQ ID NO. 11).
SEQ ID NO. 13 is an amino acid sequence of the toxin designated 1292A.
SEQ ID NO. 14 is a nucleotide sequence encoding an amino acid sequence of toxin 1292A (SEQ ID NO. 13).
SEQ ID NO. 15 is an amino acid sequence of the toxin designated 1292B.
SEQ ID NO. 16 is a nucleotide sequence encoding an amino acid sequence of toxin 1292B (SEQ ID NO. 15).
SEQ ID NO. 17 is an amino acid sequence of the toxin designated 31GA.
SEQ ID NO. 18 is a nucleotide sequence encoding an amino acid sequence of toxin 31GA (SEQ ID NO. 17).
SEQ ID NO. 19 is an amino acid sequence of the toxin designated 31GBR.
SEQ ID NO. 20 is a nucleotide sequence encoding an amino acid sequence of toxin 31GBR (SEQ ID NO. 19).
SEQ ID NO. 21 is an amino acid sequence of the toxin designated 85N1R identified by the method of the subject invention.
SEQ ID NO. 22 is a nucleotide sequence encoding an amino acid sequence of toxin 85N1R (SEQ ID NO. 21).
SEQ ID NO. 23 is an amino acid sequence of the toxin designated 85N2.
SEQ ID NO. 24 is a nucleotide sequence encoding an amino acid sequence of toxin 85N2 (SEQ ID NO. 23).
SEQ ID NO. 25 is an amino acid sequence of the toxin designated 85N3.
SEQ ID NO. 26 is a nucleotide sequence encoding an amino acid sequence of toxin 85N3 (SEQ ID NO. 25).
SEQ ID NO. 27 is an amino acid sequence of the toxin designated 86V1C1.
SEQ ID NO. 28 is a nucleotide sequence encoding an amino acid sequence of toxin 86V1C1 (SEQ ID NO. 27).
SEQ ID NO. 29 is an amino acid sequence of the toxin designated 86V1C2.
SEQ ID NO. 30 is a nucleotide sequence encoding an amino acid sequence of toxin 86V1C2 (SEQ ID NO. 29).
SEQ ID NO. 31 is an amino acid sequence of the toxin designated 86V1C3R.
SEQ ID NO. 32 is a nucleotide sequence encoding an amino acid sequence of toxin 86V1C3R (SEQ ID NO. 31).
SEQ ID NO. 33 is an amino acid sequence of the toxin designated F525A.
SEQ ID NO. 34 is a nucleotide sequence encoding an amino acid sequence of toxin F525A (SEQ ID NO. 33).
SEQ ID NO. 35 is an amino acid sequence of the toxin designated F525B.
SEQ ID NO. 36 is a nucleotide sequence encoding an amino acid sequence of toxin F525B (SEQ ID NO. 35).
SEQ ID NO. 37 is an amino acid sequence of the toxin designated F525C.
SEQ ID NO. 38 is a nucleotide sequence encoding an amino acid sequence of toxin F525C (SEQ ID NO. 37).
SEQ ID NO. 39 is an amino acid sequence of the toxin designated F573A.
SEQ ID NO. 40 is a nucleotide sequence encoding an amino acid sequence of toxin F573A (SEQ ID NO. 39).
SEQ ID NO. 41 is an amino acid sequence of the toxin designated F573B.
SEQ ID NO. 42 is a nucleotide sequence encoding an amino acid sequence of toxin F573B (SEQ ID NO. 41).
SEQ ID NO. 43 is an amino acid sequence of the toxin designated F573C.
SEQ ID NO. 44 is a nucleotide sequence encoding an amino acid sequence of toxin F573C (SEQ ID NO. 43).
SEQ ID NO. 45 is an amino acid sequence of the toxin designated FBB1A.
SEQ ID NO. 46 is a nucleotide sequence encoding an amino acid sequence of toxin FBB1A (SEQ ID NO. 45).
SEQ ID NO. 47 is an amino acid sequence of the toxin designated FBB1BR.
SEQ ID NO. 48 is a nucleotide sequence encoding an amino acid sequence of toxin FBB1BR (SEQ ID NO. 47).
SEQ ID NO. 49 is an amino acid sequence of the toxin designated FBB 1C.
SEQ ID NO. 50 is a nucleotide sequence encoding an amino acid sequence of toxin FBB1C (SEQ ID NO. 49).
SEQ ID NO. 51 is an amino acid sequence of the toxin designated FBB1D.
SEQ ID NO. 52 is a nucleotide sequence encoding an amino acid sequence of toxin FBB1D (SEQ ID NO. 51).
SEQ ID NO. 53 is an amino acid sequence of the toxin designated J31AR.
SEQ ID NO. 54 is a nucleotide sequence encoding an amino acid sequence of toxin J31AR (SEQ ID NO. 53).
SEQ ID NO. 55 is an amino acid sequence of the toxin designated J32AR.
SEQ ID NO. 56 is a nucleotide sequence encoding an amino acid sequence of toxin J32AR (SEQ ID NO. 55).
SEQ ID NO. 57 is an amino acid sequence of the toxin designated W1FAR.
SEQ ID NO. 58 is a nucleotide sequence encoding an amino acid sequence of toxin W1FAR (SEQ ID NO. 57).
SEQ ID NO. 59 is an amino acid sequence of the toxin designated W1FBR.
SEQ ID NO. 60 is a nucleotide sequence encoding an amino acid sequence of toxin W1FBR (SEQ ID NO. 59).
SEQ ID NO. 61 is an amino acid sequence of the toxin designated W1FC.
SEQ ID NO. 62 is a nucleotide sequence encoding an amino acid sequence of toxin W1FC (SEQ ID NO. 61).
SEQ ID NO. 63 is an oligonucleotide useful as a PCR primer or hybridizationprobe according to the subject invention.
SEQ ID NO. 64 is an oligonucleotide useful as a PCR primer or hybridization probe according to the subject invention.
SEQ ID NO. 65 is an oligonucleotide useful as a PCR primer or hybridizationprobe according to the subject invention.
SEQ ID NO. 66 is an oligonucleotide useful as a PCR primer or hybridizationprobe according to the subject invention.
SEQ ID NO. 67 is an oligonucleotide useful as a PCR primer or hybridizationprobe according to the subject invention.
SEQ ID NO. 68 is an oligonucleotide useful as a PCR primer or hybridizationprobe according to the subject invention.
SEQ ID NO. 69 is an oligonucleotide useful as a PCR primer or hybridizationprobe according to the subject invention.
SEQ ID NO. 70 is an amino acid sequence of the toxin designated 86BB1(a).
SEQ ID NO. 71 is a nucleotide sequence encoding an amino acid sequence of toxin 86BB1(a).
SEQ ID NO. 72 is an amino acid sequence of the toxin designated 86BB1(b).
SEQ ID NO. 73 is a nucleotide sequence encoding an amino acid sequence of toxin 86BB1(b).
SEQ ID NO. 74 is an amino acid sequence of the toxin designated 31G1(a).
SEQ ID NO. 75 is a nucleotide sequence encoding an amino acid sequence of toxin 31G1(a).
SEQ ID NO. 76 is an amino acid sequence of the toxin designated 129HD chimeric.
SEQ ID NO. 77 is a nucleotide sequence encoding an amino acid sequence of toxin 129HD chimeric.
SEQ ID NO. 78 is an amino acid sequence of the toxin designated 11B(a).
SEQ ID NO. 79 is a nucleotide sequence encoding an amino acid sequence of toxin 11B(a).
SEQ ID NO. 80 is an amino acid sequence of the toxin designated 31G1(b).
SEQ ID NO. 81 is a nucleotide sequence encoding an amino acid sequence of toxin 31G1(b).
SEQ ID NO. 82 is an amino acid sequence of the toxin designated 86BB1(c).
SEQ ID NO. 83 is a nucleotide sequence encoding an amino acid sequence of toxin 86BB1(c).
SEQ ID NO. 84 is an amino acid sequence of the toxin designated 86V1(a).
SEQ ID NO. 85 is a nucleotide sequence encoding an amino acid sequence of toxin 86V1(a).
SEQ ID NO. 86 is an amino acid sequence of the toxin designated 86W1(a).
SEQ ID NO. 87 is a nucleotide sequence encoding an amino acid sequence of toxin 86W1(a).
SEQ ID NO. 88 is a partial amino acid sequence of the toxin designated 94R1(a).
SEQ ID NO. 89 is a partial nucleotide sequence encoding an amino acid sequence of toxin 94R1(a).
SEQ ID NO. 90 is an amino acid sequence of the toxin designated 185U2(a).
SEQ ID NO. 91 is a nucleotide sequence encoding an amino acid sequence of toxin 185U2(a).
SEQ ID NO. 92 is an amino acid sequence of the toxin designated 202S(a).
SEQ ID NO. 93 is a nucleotide sequence encoding an amino acid sequence of toxin 202S(a).
SEQ ID NO. 94 is an amino acid sequence of the toxin designated 213E5(a).
SEQ ID NO. 95 is a nucleotide sequence encoding an amino acid sequence of toxin 213E5(a).
SEQ ID NO. 96 is an amino acid sequence of the toxin designated 218G2(a).
SEQ ID NO. 97 is a nucleotide sequence encoding an amino acid sequence of toxin 218G2(a).
SEQ ID NO. 98 is an amino acid sequence of the toxin designated 29HD(a).
SEQ ID NO. 99 is a nucleotide sequence encoding an amino acid sequence of toxin 29HD(a).
SEQ ID NO. 100 is an amino acid sequence of the toxin designated 110HD(a).
SEQ ID NO. 101 is a nucleotide sequence encoding an amino acid sequence of toxin 110HD(a).
SEQ ID NO. 102 is an amino acid sequence of the toxin designated 129HD(b).
SEQ ID NO. 103 is a nucleotide sequence encoding an amino acid sequence of toxin 129HD(b).
SEQ ID NO. 104 is a partial amino acid sequence of the toxin designated 573HD(a).
SEQ ID NO. 105 is a partial nucleotide sequence encoding an amino acid sequence of toxin 573HD(a).
The subject invention concerns materials and methods for the control of non-mammalian pests. In specific embodiments, the subject invention pertains to new Bacillus thuringiensis isolates and toxins which have activity against lepidopterans. In a particularly preferred embodiment, the toxins and methodologies described herein can be used to control black cutworm. The subject invention further concerns novel genes which encode pesticidal toxins and novel methods for identifying and characterizing B.t. genes which encode toxins with useful properties. The subject invention concerns not only the polynucleotide sequences which encode these toxins, but also the use of these polynucleotide sequences to produce recombinant hosts which express the toxins.
Certain proteins of the subject invention are distinct from the crystal or xe2x80x9cCryxe2x80x9d proteins which have previously been isolated from Bacillus thuringiensis. 
A further aspect of the subject invention concerns novel isolates and the toxins and genes obtainable from these isolates. The novel B.t. isolates of the subject invention have been designated PS31G1, PS185U2, PS11B, PS218G2, PS213E5, PS28C, PS86BB1, PS89J3, PS94R1, PS202S, PS101DD, and PS27J2.
The new toxins and polynucleotide sequences provided here are defined according to several parameters. One critical characteristic of the toxins described herein is pesticidal activity. In a specific embodiment these toxins have activity against lepidopteranpests. The toxins and genes of the subject invention can be further defined by their amino acid and nucleotide sequences. The sequences of the molecules can be defined in terms of homology to certain exemplified sequences as well as in terms of the ability to hybridize with, or be amplified by, certain exemplified probes and primers. The toxins provided herein can also be identified based on their immunoreactivity with certain antibodies.
Methods have been developed for making useful chimeric toxins by combining portions of B.t. crystal proteins. The portions which are combined need not, themselves, be pesticidal so long as the combination of portions creates a chimeric protein which is pesticidal. This can be done using restriction enzymes, as described in, for example, European Patent 0 228 838; Ge, A. Z., N. L. Shivarova, D. H. Dean (1989) Proc. Natl. Acad. Sci. USA 86:4037-4041; Ge, A. Z., D. Rivers, R. Milne, D. H. Dean (1991) J. Biol. Chem. 266:17954-17958; Schnepf, H. E., K. Tomezak, J. P. Ortega, H. R. whiteley (1990) J. Biol. Chem. 265:20923-20930; Honee, G., D. Convents, J. Van Rie, S. Jansens, M. Peferoen, B. Visser (1991) Mol. Microbiol. 5:2799-2806. Alternatively, recombination using cellular recombination mechanisms can be used to achieve similar results. See, for example, Caramori, T., A. M. Albertini, A. Galizzi (1991) Gene 98:37-44; Widner, W. R., H. R. Whiteley (1990) J. Bacteriol. 172:2826-2832; Bosch, D., B. Schipper,H. van derKliej, R. A. de Maagd, W. J. Stickema (1994) Biotechnology 12:915-918. A number of other methods are known in the art by which such chimeric DNAs can be made. The subject invention is meant to include chimeric proteins that utilize the novel sequences identified in the subject application.
With the teachings provided herein, one skilled in the art could readily produce and use the various toxins and polynucleotide sequences described herein.
B.t. isolates useful according to the subject invention have been deposited in the permanent collection of the Agricultural Research Service Patent Culture Collection (NRRL), Northern Regional Research Center, 1 815 North University Street, Peoria, Ill. 61604, USA. The culture repository numbers of the B.t. strains are as follows:
Cultures which have been deposited for the purposes of this patent application were deposited under conditions that assure that access to the cultures is available during the pendency of this patent application to one determined by the Commissioner of Patents and Trademarksto be entitled thereto under 37 CFR 1.14 and 35 U.S.C. 122. The deposits will be available as required by foreign patent laws in countries wherein counterparts of the subject application, or its progeny, are filed. However, it should be understood that the availability of a deposit does not constitute a license to practice the subject invention in derogation of patent rights granted by governmental action.
Further, the subject culture deposits will be stored and made available to the public in accord with the provisions of the Budapest Treaty for the Deposit of Microorganisms, i.e., they will be stored with all the care necessary to keep them viable and uncontaminated for a period of at least five years after the most recent request for the furnishing of a sample of the deposit, and in any case, for a period of at least thirty (30) years after the date of deposit or for the enforceable life of any patent which may issue disclosing the culture(s). The depositor acknowledges the duty to replace the deposit(s) should the depository be unable to furnish a sample when requested, due to the condition of a deposit. All restrictions on the availability to the public of the subject culture deposits will be irrevocably removed upon the granting of a patent disclosing them.
Following is a table which provides characteristics of certain isolates useful according to the subject invention.
In one embodiment, the subject invention concerns materials and methods including nucleotide primers and probes for isolating and identifying Bacillus thuringiensis (B.t.) genes encoding protein toxins which are active against lepidopteran pests. The nucleotide sequences described herein can also be used to identify new pesticidal B.t. isolates. The invention further concerns the genes, isolates, and toxins identified using the methods and materials disclosed herein.
Genes and toxins. The genes and toxins useful according to the subject invention include not only the full length sequences but also fragments of these sequences, variants, mutants, and fusion proteins which retain the characteristic pesticidal activity of the toxins specifically exemplified herein. Chimeric genes and toxins, producedby combiningportions from more than one B.t. toxin or gene, may also be utilized according to the teachings of the subject invention. As used herein, the terms xe2x80x9cvariantsxe2x80x9d or xe2x80x9cvariationsxe2x80x9d of genes refer to nucleotide sequences which encode the same toxins or which encode equivalent toxins having pesticidal activity. As used herein, the term xe2x80x9cequivalent toxinsxe2x80x9d refers to toxins having the same or essentially the same biological activity against the target pests as the exemplified toxins.
It should be apparent to a person skilled in this art that genes encoding active toxins can be identified and obtained through several means. The specific genes exemplified herein may be obtained from the isolates deposited at a culture depository as described above. These genes, or portions or variants thereof, may also be constructed synthetically, for example, by use of a gene synthesizer. Variations of genes may be readily constructedusing standard techniques for making point mutations. Also, fragments of these genes can be made using commercially available exonucleases or endonucleases according to standard procedures. For example, enzymes such as Bal31 or site-directed mutagenesis can be used to systematicallycut off nucleotides from the ends of these genes. Also, genes which encode active fragments may be obtained using a variety of restriction enzymes. Proteases may be used to directly obtain active fragments of these toxins.
Equivalent toxins and/or genes encoding these equivalent toxins can be derived from B.t. isolates and/or DNA libraries using the teachings provided herein. There are a number of methods for obtaining the pesticidal toxins of the instant invention. For example, antibodies to the pesticidal toxins disclosed and claimed herein can be used to identify and isolate other toxins from a mixture of proteins. Specifically, antibodies may be raised to the portions of the toxins which are most constant and most distinct from other B.t. toxins. These antibodies can then be used to specifically identify equivalent toxins with the characteristic activity by immunoprecipitation, enzyme linked immunosorbent assay (ELISA), or western blotting. Antibodies to the toxins disclosed herein, or to equivalent toxins, or fragments of these toxins, can readily be prepared using standard procedures in this art. The genes which encode these toxins can then be obtained from the microorganism.
Fragments and equivalents which retain the pesticidal activity of the exemplified toxins would be within the scope of the subject invention. Also, because of the redundancy of the genetic code, a variety of different DNA sequences can encode the amino acid sequences disclosed herein. It is well within the skill of a person trained in the art to create these alternative DNA sequences encoding the same, or essentially the same, toxins. These variant DNA sequences are within the scope of the subject invention. As used herein, reference to xe2x80x9cessentially the samexe2x80x9d sequence refers to sequences which have amino acid substitutions, deletions, additions, or insertions which do not materially affect pesticidal activity. Fragments retaining pesticidal activity are also included in this definition.
A further method for identifying the toxins and genes of the subject invention is through the use of oligonucleotideprobes. These probes are detectable nucleotide sequences. Probes provide a rapid method for identifying toxin-encoding genes of the subject invention. The nucleotide segments which are used as probes according to the invention can be synthesized using a DNA synthesizer and standard procedures.
Certain toxins of the subject invention have been specifically exemplified herein. Since these toxins are merely exemplary of the toxins of the subject invention, it should be readily apparent that the subject invention comprises variant or equivalent toxins (and nucleotide sequences coding for equivalent toxins) having the same or similar pesticidal activity of the exemplified toxin. Equivalent toxins will have amino acid homology with an exemplified toxin. This amino acid identity will typically be greater than 60%, preferably be greater than 75%, more preferably greater than 80%, more preferably greater than 90%, and can be greater than 95%. The amino acid homology will be highest in critical regions of the toxin which account for biological activity or are involved in the determination of three-dimensional configuration which ultimately is responsible for the biological activity. In this regard, certain amino acid substitutions are acceptable and can be expected if these substitutions are in regions which are not critical to activity or are conservative amino acid substitutions which do not affect the three-dimensional configuration of the molecule. For example, amino acids may be placed in the following classes: non-polar, uncharged polar, basic, and acidic. Conservative substitutions whereby an amino acid of one class is replaced with another amino acid of the same type fall within the scope of the subject invention so long as the substitution does not materially alter the biological activity of the compound. Table 2 provides a listing of examples of amino acids belonging to each class.
In some instances, non-conservative substitutions can also be made. The critical factor is that these substitutions must not significantly detract from the biological activity of the toxin.
The toxins of the subject invention can also be characterized in terms of the shape and location of toxin inclusions, which are described above.
As used herein, reference to xe2x80x9cisolatedxe2x80x9d polynucleotides and/or xe2x80x9cpurifiedxe2x80x9d toxins refers to these molecules when they are not associated with the other molecules with which they would be found in nature. Thus, xe2x80x9cpurifiedxe2x80x9d toxins would include, for example, the subject toxins expressed in plants. Reference to xe2x80x9cisolated and purifiedxe2x80x9d signifies the involvement of the xe2x80x9chand of manxe2x80x9d as described herein. Chimeric toxins and genes also involve the xe2x80x9chand of man.xe2x80x9d
Recombinant hosts. The toxin-encoding genes harbored by the isolates of the subject invention can be introduced into a wide variety of microbial or plant hosts. Expression of the toxin gene results, directly or indirectly, in the intracellular production and maintenance of the pesticide. With suitable microbial hosts, e.g., Pseudomonas, the microbes can be applied to the situs of the pest, where they will proliferate and be ingested. The result is a control of the pest. Altematively,the microbe hosting the toxin gene can be treated under conditions that prolong the activity of the toxin and stabilize the cell. The treated cell, which retains the toxic activity, then can be applied to the environment of the target pest.
Where the B.t. toxin gene is introduced via a suitable vector into a microbial host, and said host is applied to the environment in a living state, it is essential that certain host microbes be used. Microorganism hosts are selected which are known to occupy the xe2x80x9cphytospherexe2x80x9d (phylloplane, phyllosphere, rhizosphere, and/or rhizoplane) of one or more crops of interest. These microorganisms are selected so as to be capable of successfully competing in the particular environment (crop and other insect habitats) with the wild-type microorganisms, provide for stable maintenance and expression of the gene expressing the polypeptide pesticide, and, desirably, provide for improved protection of the pesticide from environmental degradation and inactivation.
A large number of microorganisms are known to inhabit the phylloplane (the surface of the plant leaves) and/or the rhizosphere (the soil surrounding plant roots) of a wide variety of important crops. These microorganismsinclude bacteria, algae, and fungi. Of particular interest are microorganisms, such as bacteria, e.g., genera Pseudomonas, Erwinia, Serratia, Klebsiella, Xanthomonas, Streptomyces, Rhizobium, Rhodopseudomonas, Methylophilius, Agrobacterium, Acetobacter, Lactobacillus, Arthrobacter, Azotobacter, Leuconostoc, and Alcaligenes; fungi, particularly yeast, e.g., genera Saccharomyces, Cryptococcus, Kluyveromyces, Sporobolomyces, Rhodotorula, and Aureobasidium. Of particular interest are such phytosphere bacterial species as Pseudomonas syringae, Pseudomonasfluorescens, Serratia marcescens, Acetobacterxylinum, Agrobacterium tumefaciens, Rhodopseudomonas spheroides, Xanthomonas campestris, Rhizobium melioti, Alcaligenes entrophus, and Azotobacter vinlandii; and phytosphere yeast species such as Rhodotorula rubra, R. glutinis, R. marina, R. aurantiaca, Cryptococcus albidus, C. diffluens, C. iaurentii, Saccharomyces rosei, S. pretoriensis, S. cerevisiae, Sporobolomyces roseus, S. odorus, Kluyveromyces veronae, and Aureobasidium pollulans. Of particular interest are the pigmented microorganisms.
A wide variety of ways are available for introducing a B.t. gene encoding a toxin into a microorganism host under conditions which allow for stable maintenance and expression of the gene. These methods are well known to those skilled in the art and are described, for example, in U.S. Pat. No. 5,135,867, which is incorporated herein by reference.
Control of lepidopterans, including black cutworm, using the isolates, toxins, and genes of the subject invention can be accomplished by a variety of methods known to those skilled in the art. These methods include, for example, the application of B.t. isolates to the pests (or their location), the application of recombinant microbes to the pests (or their locations), and the transformation of plants with genes which encode the pesticidal toxins of the subject invention. Recombinant microbes may be, for example, a B.t., E. coli., or Pseudomonas. Transformations can be made by those skilled in the art using standard techniques. Materials necessary for these transformations are disclosed herein or are otherwise readily available to the skilled artisan. Synthetic genes which are functionally equivalent to the toxins of the subject invention can also be used to transformed hosts. Methods for the production of synthetic genes can be found in, for example, U.S. Pat. No. 5,380,831.
Treatment of cells. As mentioned above, B.t. or recombinant cells expressing a B.t. toxin can be treated to prolong the toxin activity and stabilize the cell. The pesticide microcapsule that is formed comprises the B.t. toxin within a cellular structure that has been stabilized and will protect the toxin when the microcapsule is applied to the environment of the target pest. Suitable host cells may include either prokaryotes or eukaryotes, normally being limited to those cells which do not produce substances toxic to higher organisms, such as mammals. However, organisms which produce substances toxic to higher organisms could be used, where the toxic substances are unstable or the level of application sufficiently low as to avoid any possibility of toxicity to a mammalian host. As hosts, of particular interest will be the prokaryotes and the lower eukaryotes, such as fungi.
The cell will usually be intact and be substantially in the proliferative form when treated, rather than in a spore form, although in, some instances spores may be employed. Treatment of the microbial cell, e.g., a microbe containing the B.t. toxin gene, can be by chemical or physical means, or by a combination of chemical and/or physical means, so long as the technique does not deleteriously affect the properties of the toxin, nor diminish the cellular capability of protecting the toxin. Examples of chemical reagents are halogenating agents, particularly halogens of atomic no. 17-80. More particularly, iodine can be used under mild conditions and for sufficient time to achieve the desired results. Other suitable techniques include treatment with aldehydes, such as glutaraldehyde; anti-infectives, such as zephiran chloride and cetylpyridinium chloride; alcohols, such as isopropyl and ethanol; various histologic fixatives, such as Lugol iodine, Bouin""s fixative, various acids and Helly""s fixative (See: Humason, Gretchen L., Animal Tissue Techniques, W. H. Freeman and Company, 1967); or a combination of physical (heat) and chemical agents that preserve and prolong the activity of the toxin produced in the cell when the cell is administered to the host environment. Examples of physical means are short wavelength radiation such as gamma-radiation and X-radiation, freezing, UV irradiation, lyophilization, and the like. Methods for treatment of microbial cells are disclosed in U.S. Pat. Nos. 4,695,455 and 4,695,462, which are incorporated herein by reference.
The cells generally will have enhanced structural stability which will enhance resistance to environmental conditions. Where the pesticide is in a proform, the method of cell treatment should be selected so as not to inhibit processing of the proform to the mature form of the pesticide by the target pest pathogen. For example, formaldehyde will crosslink proteins and could inhibit processing of the proform of a polypeptide pesticide. The method of treatment should retain at least a substantial portion of the bio-availability or bioactivity of the toxin.
Characteristics of particular interest in selecting a host cell for purposes of production include ease of introducing the B.t. gene into the host, availability of expression systems, efficiency of expression, stability of the pesticide in the host, and the presence of auxiliary genetic capabilities. Characteristics of interest for use as a pesticide microcapsule include protective qualities for the pesticide, such as thick cell walls, pigmentation, and intracellular packaging or formation of inclusion bodies; survival in aqueous environments; lack of mammalian toxicity; attractiveness to pests for ingestion; ease of killing and fixing without damage to the toxin; and the like. Other considerations include ease of formulation and handling, economics, storage stability, and the like.
Growth of cells. The cellular host containing the B.t. insecticidal gene may be grown in any convenient nutrient medium, where the DNA construct provides a selective advantage, providing for a selective medium so that substantially all or all of the cells retain the B.t. gene. These cells may then be harvested in accordance with conventional ways. Alternatively, the cells can be treated prior to harvesting.
The B.t. cells of the invention can be cultured using standard art media and fermentation techniques. Upon completion of the fermentation cycle the bacteria can be harvested by first separating the B.t. spores and crystals from the fermentation broth by means well known in the art. The recovered B.t. spores and crystals can be formulated into a wettable powder, liquid concentrate, granules or other formulations by the addition of surfactants, dispersants, inert carriers, and other components to facilitate handling and application for particular target pests. These formulations and application procedures are all well known in the art.
Methods and formulations for control of pests. Control of lepidopterans using the isolates, toxins, and genes of the subject invention can be accomplished by a variety of methods known to those skilled in the art. These methods include, for example, the application of B.t. isolates to the pests (or their location), the application of recombinant microbes to the pests (or their locations), and the transformation of plants with genes which encode the pesticidal toxins of the subject invention. Recombinant microbes may be, for example, a B.t., E. coli, or Pseudomonas. Transformations can be made by those skilled in the art using standard techniques. Materials necessary for these transformations are disclosed herein or are otherwise readily available to the skilled artisan.
Formulated bait granules containing an attractant and spores and crystals of the B.t. isolates, or recombinant microbes comprising the genes obtainable from the B.t. isolates disclosed herein, can be applied to the soil. Formulated product can also be applied as a seed-coating or root treatment or total plant treatment at later stages of the crop cycle. Plant and soil treatments of B.t. cells may be employed as wettable powders, granules or dusts, by mixing with various inert materials, such as inorganic minerals (phyllosilicates, carbonates, sulfates, phosphates, and the like) or botanical materials (powdered corncobs, rice hulls, walnut shells, and the like). The formulations may include spreader-sticker adjuvants, stabilizing agents, other pesticidal additives, or surfactants. Liquid formulations may be aqueous-based or non-aqueous and employed as foams, gels, suspensions, emulsifiable concentrates, or the like. The ingredients may include Theological agents, surfactants, emulsifiers, dispersants, or polymers.
As would be appreciated by a person skilled in the art, the pesticidal concentration will vary widely depending upon the nature of the particular formulation, particularly whether it is a concentrate or to be used directly. The pesticide will be present in at least 1% by weight and may be 100% by weight. The dry formulations will have from about 1-95% by weight of the pesticide while the liquid formulations will generally be from about 1-60% by weight of the solids in the liquid phase. The formulations will generally have from about 102 to about 104 cells/mg. These formulations will be administered at about 50 mg (liquid or dry) to 1 kg or more per hectare.
The formulations can be applied to the environment of the pest, e.g., soil and foliage, by spraying, dusting, sprinkling, or the like.
Mutants. Mutants of the isolates of the invention can be made by procedures well known in the art- For example, an asporogenous mutant can be obtained through ethylmethane sulfonate (EMS) mutagenesis of an isolate. The mutants can be made using ultraviolet light and nitrosoguanidine by procedures well known in the art.
A smaller percentage of the asporogenous mutants will remain intact and not lyse for extended fermentation periods; these strains are designated lysis minus (xe2x88x92). Lysis minus strains can be identified by screening asporogenous mutants in shake flask media and selecting those mutants that are still intact and contain toxin crystals at the end of the fermentation. Lysis minus strains are suitable for a cell treatment process that will yield a protected, encapsulated toxin protein.
To prepare a phage resistant variant of said asporogenous mutant, an aliquot of the phage lysate is spread onto nutrient agar and allowed to dry. An aliquot of the phage sensitive bacterial strain is then plated directly over the dried lysate and allowed to dry. The plates are incubated at 30xc2x0 C. The plates are incubated for 2 days and, at that time, numerous colonies could be seen growing on the agar. Some of these colonies are picked and subcultured onto nutrient agar plates. These apparent resistant cultures are tested for resistance by cross streaking with the phage lysate. A line of the phage lysate is streaked on the plate and allowed to dry. The presumptive resistant cultures are then streaked across the phage line. Resistant bacterial cultures show no lysis anywhere in the streak across the phage line after overnight incubation at 30xc2x0 C. The resistance to phage is then reconfirmed by plating a lawn of the resistant culture onto a nutrient agar plate. The sensitive strain is also plated in the same manner to serve as the positive control. After drying, a drop of the phage lysate is placed in the center of the plate and allowed to dry. Resistant cultures showed no lysis in the area where the phage lysate has been placed after incubation at 30xc2x0 C. for 24 hours.
Polynucleotide probes. It is well known that DNA possesses a fundamental property called base complementarity. In nature, DNA ordinarily exists in the form of pairs of anti-parallel strands, the bases on each strand projecting from that strand toward the opposite strand. The base adenine (A) on one strand will always be opposed to the base thymine (T) on the other strand, and the base guanine (G) will be opposed to the base cytosine (C). The bases are held in apposition by their ability to hydrogen bond in this specific way. Though each individual bond is relatively weak, the net effect of many adjacent hydrogen bonded bases, together with base stacking effects, is a stable joining of the two complementary strands. These bonds can be broken by treatments such as high pH or high temperature, and these conditions result in the dissociation, or xe2x80x9cdenaturation,xe2x80x9d of the two strands. If the DNA is then placed in conditions which make hydrogen bonding of the bases thermodynamically favorable, the DNA strands will anneal, or xe2x80x9chybridize,xe2x80x9d and reform the original double stranded DNA. If carried out under appropriate conditions, this hybridization can be highly specific. That is, only strands with a high degree of base complementarity will be able to form stable double stranded structures. The relationship of the specificity of hybridization to reaction conditions is well known. Thus, hybridization may be used to test whether two pieces of DNA are complementary in their base sequences. It is this hybridization mechanism which facilitates the use of probes of the subject invention to readily detect and characterize DNA sequences of interest.
The probes may be RNA or DNA. The probe will normally have at least about 10 bases, more usually at least about 18 bases, and may have up to about 50 bases or more, usually not having more than about 200 bases if the probe is made synthetically. However, longer probes can readily be utilized, and such probes can be, for example, several kilobases in length. The probe sequence is designed to be at least substantially complementary to a gene encoding a toxin of interest. The probe need not have perfect complementarity to the sequence to which it hybridizes. The probes may be labelled utilizing techniques which are well known to those skilled in this art.
One approach for the use of the subject invention as probes entails first identifying by Southern blot analysis of a gene bank of the B.t. isolate all DNA segments homologous with the disclosed nucleotide sequences. Thus, it is possible, without the aid of biological analysis, to know in advance the probable activity of many new B.t. isolates, and of the individual endotoxin gene products expressed by a given B.t. isolate. Such a probe analysis provides a rapid method for identifying potentially commercially valuable insecticidal endotoxin genes within the multifarious subspecies of B.t. 
One hybridization procedure useful according to the subject invention typically includes the initial steps of isolating the DNA sample of interest and purifying it chemically. Either lysed bacteria or total fractionated nucleic acid isolated from bacteria can be used. Cells can be treated using known techniques to liberate their DNA (and/or RNA). The DNA sample can be cut into pieces with an appropriate restriction enzyme. The pieces can be separated by size through electrophoresisin a gel, usually agarose or acrylamide. The pieces of interest can be transferred to an immobilizing membrane in a manner that retains the geometry of the pieces. The membrane can then be dried and prehybridized to equilibrate it for later immersion in a hybridization solution. The manner in which the nucleic acid is affixed to a solid support may vary. This fixing of the DNA for later processing has great value for the use of this technique in field studies, remote from laboratory facilities.
The particular hybridization technique is not essential to the subject invention. As improvements are made in hybridization techniques, they can be readily applied.
As is well known in the art, if the probe molecule and nucleic acid sample hybridize by forming a strong non-covalent bond between the two molecules, it can be reasonably assumed that the probe and sample are essentially identical. The probe""s detectable label provides a means for determining in a known manner whether hybridization has occurred.
The nucleotide segments of the subject invention which are used as probes can be synthesized by use of DNA synthesizers using standard procedures. In the use of the nucleotide segments as probes, the particular probe is labeled with any suitable label known to those skilled in the art, including radioactive and non-radioactive labels. Typical radioactive labels include 32P, 35S, or the like. A probe labeled with a radioactive isotope can be constructed from a nucleotide sequence complementary to the DNA sample by a conventional nick translation reaction, using a DNase and DNA polymerase. The probe and sample can then be combined in a hybridization buffer solution and held at an appropriate temperature until annealing occurs. Thereafter, the membrane is washed free of extraneous materials, leaving the sample and bound probe molecules typically detected and quantified by autoradiography and/or liquid scintillation counting. For synthetic probes, it may be most desirable to use enzymes such as polynucleotide kinase or terminal transferase to end-label the DNA for use as probes.
Non-radioactive labels include, for example, ligands such as biotin or thyroxine, as well as enzymes such as hydrolases or perixodases, or the various chemiluminescers such as luciferin, or fluorescent compounds like fluorescein and its derivatives. The probes may be made inherently fluorescent as described in International Application No. WO93/16094. The probe may also be labeled at both ends with different types of labels for ease of separation, as, for example, by using an isotopic label at the end mentioned above and a biotin label at the other end.
The amount of labeled probe which is present in the hybridization solution will vary widely, depending upon the nature of the label, the amount of the labeled probe which can reasonably bind to the filter, and the stringency of the hybridization. Generally, substantial excesses of the probe will be employed to enhance the rate of binding of the probe to the fixed DNA.
Various degrees of stringency of hybridization can be employed. The more severe the conditions, the greater the complementarity that is required for duplex formation. Severity can be controlled by temperature, probe concentration, probe length, ionic strength, time, and the like. Preferably, hybridization is conducted under stringent conditions by techniques well known in the art, as described, for example, in Keller, G. H., M. M. Manak (1987) DNA Probes, Stockton Press, New York, N.Y., pp. 169-170. For example, as stated therein, the labeled probe and the target nucleic acid are allowed to hybridize overnight at 42xc2x0 C. in hybridization buffer of 50% deionized formamide, 5xc3x97SSC (Standard Saline Citrate), 1xc3x97Denhardt""s solution, 31 mM KH2PO4, 0.25% SDS (Sodium Dodecyl Sulfate), 30 xcexcg/ml sheared/denatured salmon sperm DNA, and 5% dextran sulfate. In order to remove unhybridized probe, high stringency washes can be conducted with 0.1xc3x97SSC (Standard Saline Citrate)/0.1% SDS (Sodium Dodecyl Sulfate) for 15 minutes at 55xc2x0 C.
As used herein xe2x80x9cstringentxe2x80x9d conditions for hybridization refers to conditions which achieve the same, or about the same, degree of specificity of hybridization as the conditions employed by the current applicants. Specifically, hybridization of immobilized DNA on Southern blots with 32P-labeled gene-specific probes was performed by standard methods (Maniatis, T., E. F. Fritsch, J. Sambrook [1982] Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.). In general, hybridization and subsequent washes were carried out under stringent conditions that allowed for detection of target sequences with homology to the exemplified toxin genes. For double-stranded DNA gene probes, hybridization was carried out overnight at 20-25xc2x0 C. below the melting temperature (Tm) of the DNA hybrid in 6xc3x97SSPE, 5xc3x97Denhardt""s solution, 0.1% SDS, 0.1 mg/ml denatured DNA. The melting temperature is described by the following formula (Beltz, G. A., K. A. Jacobs, T. H. Eickbush, P. T. Cherbas, and F. C. Kafatos [1983] Methods of Enzymology, R. Wu, L. Grossman and K. Moldave [eds.] Academic Press, New York 100:266-285).
Tm=81.5xc2x0 C.+16.6 Log[Na+]+0.41(% G+C)xe2x88x920.61 (% formamide)xe2x88x92600/length of duplex in base pairs.
Washes are typically carried out as follows:
(1) Twice at room temperature for 15 minutes in 1xc3x97SSPE, 0.1% SDS (low stringency wash).
(2) Once at Tm-20xc2x0 C. for 15 minutes in 0.2xc3x97SSPE, 0.1% SDS (moderate stringency wash).
For oligonucleotide probes, hybridization was carried out overnight at 10-20xc2x0 C. below the melting temperature (Tm) of the hybrid in 6xc3x97SSPE, 5xc3x97Denhardt""s solution, 0.1% SDS, 0.1 mg/ml denatured DNA. Tm for oligonucleotide probes was determined by the following formula:
Tm (xc2x0 C.)=2(number T/A base pairs)+4(number GIC base pairs) (Suggs, S. V., T. Miyake, E. H. Kawashime, M. J. Johnson, K. Itakura, and R. B. Wallace [1981] ICN-UCLA Symp. Dev. Biol. Using Purified Genes, D. D. Brown [ed.], Academic Press, New York, 23:683-693).
Washes were typically carried out as follows:
(1) Twice at room temperature for 15 minutes 1xc3x97SSPE, 0.1% SDS (low stringency wash).
(2) Once at the hybridization temperature for 15 minutes in 1xc3x97SSPE, 0.1% SDS (moderate stringency wash).
Duplex formation and stability depend on substantial complementarity between the two strands of a hybrid, and, as noted above, a certain degree of mismatch can be tolerated. Therefore, the nucleotide sequences of the subject invention include mutations (both single and multiple), deletions, insertions of the described sequences, and combinations thereof, wherein said mutations, insertions and deletions permit formation of stable hybrids with the target polynucleotide of interest. Mutations, insertions, and deletions can be produced in a given polynucleotide sequence in many ways, and these methods are known to an ordinarily skilled artisan. Other methods may become known in the future.
The known methods include, but are not limited to:
(1) synthesizing chemically or otherwise an artificial sequence which is a mutation, insertion or deletion of the known sequence;
(2) using a nucleotide sequence of the present invention as a probe to obtain via hybridization a new sequence or a mutation, insertion or deletion of the probe sequence; and
(3) mutating, inserting or deleting a test sequence in vitro or in vivo.
It is important to note that the mutational, insertional, and deletional variants generated from a given probe may be more or less efficient than the original probe. Notwithstanding such differences in efficiency, these variants are within the scope of the present invention.
Thus, mutational, insertional, and deletional variants of the disclosed nucleotide sequences can be readily prepared by methods which are well known to those skilled in the art. These variants can be used in the same manner as the exemplified primer sequences so long as the variants have substantial sequence homology with the original sequence. As used herein, substantial sequence homology refers to homology which is sufficient to enable the variant to function in the same capacity as the original probe. Preferably, this homology is greater than 50%; more preferably,this homology is greater than 75%; and most preferably, this homology is greater than 90%. The degree of homology needed for the variant to function in its intended capacity will depend upon the intended use of the sequence. It is well within the skill of a person trained in this art to make mutational, insertional, and deletional mutations which are designed to improve the function of the sequence or otherwise provide a methodological advantage.
PCR technology. Polymerase Chain Reaction (PCR) is a repetitive, enzymatic, primed synthesis of a nucleic acid sequence. This procedure is well known and commonly used by those skilled in this art (see Mullis, U.S. Pat. Nos. 4,683,195, 4,683,202, and 4,800,159; Saiki, Randall K., Stephen Scharf, Fred Faloona, Kary B. Mullis, Glenn T. Horn, Henry A. Erlich, Norman Anheirn [1985] xe2x80x9cEnzymaticAmplification of xcex2-Globin Genomic Sequences and Restriction Site Analysis for Diagnosis of Sickle Cell Anemia,xe2x80x9d Science 230:1350-1354.). PCR is based on the enzymatic amplification of a DNA fragment of interest that is flanked by two oligonucleotide primers that hybridize to opposite strands of the target sequence. The primers are oriented with the 3xe2x80x2 ends pointing towards each other. Repeated cycles of heat denaturation of the template, annealing of the primers to their complementary sequences, and extension of the annealed primers with a DNA polymerase result in the amplification of the segment defined by the 5xe2x80x2 ends of the PCR primers. Since the extension product of each primer can serve as a template for the other primer, each cycle essentially doubles the amount of DNA fragment produced in the previous cycle. This results in the exponential accumulation of the specific target fragment, up to several million-fold in a few hours. By using a thermostable DNA polymerase such as Taq polymerase, which is isolated from the thermophilic bacterium Thermus aquaticus, the amplification process can be completely automated.
The DNA sequences of the subject invention can be used as primers for PCR amplification. In performing PCR amplification, a certain degree of mismatch can be tolerated between primer and template. Therefore, mutations, deletions, and insertions (especially additions of nucleotides to the 5xe2x80x2 end) of the exemplified primers fall within the scope of the subject invention. Mutations, insertions and deletions can be produced in a given primer by methods known to an ordinarily skilled artisan. It is important to note that the mutational, insertional, and deletional variants generated from a given primer sequence may be more or less efficient than the original sequences. Not with standing such differences in efficiency, these variants are within the scope of the present invention.